Posts Tagged ‘maintenance’

1 Sustainability & Maintenance

1.1 Environmental Impact of Materials

1.1.1 Timber and Deforestation

Because the MFB uses wood from trees that is being sourced from Cambodia, deforestation will be a direct result of the selection of timber.

v Negative aspects of deforestation is that it destroys the natural habitats of local flora and fauna that are unable to survive in an adversely different localized environment, due to both the different habit and climate conditions that arise (Telepool, 2008). Deforestation results in an increase in ground temperature, as a direct result of there being no physical coverage provided by trees. Soil will become significantly drier compared to the original moist soil conditions. A lower extent of carbon dioxide to oxygen exchange will result. Note however, the negative aspects of deforestation can be counteracted by the growing of more trees (North Carolina Christmas Tree Association, 2008).

v Positive aspects of using timber (and re-growing trees once the trees have been chopped down) is that throughout its lifecycle, a tree intakes carbon dioxide and releases this as oxygen through a process known as photosynthesis (Smith, 1997). Even when the tree is eventually cut down, the carbon is “locked” in the tissue and wood of the tree, until it is burnt, when it will react with the oxygen in the air (Current.com, 2009). Thus, you’re helping the environment!

Obviously, the issue is when deforestation occurs at a more rapid rate than forestation (which is a common occurrence since it takes longer to grow a tree than it does to chop it down). Nevertheless, in the long haul, as described in 2.1.1, self-use of Cambodian resources will increase the demand for wood, thus increase the price of woods, reducing price competitiveness, thus eventually, demand for Cambodian wood.

1.1.2 Marine Impacts

There are no predicted long-term effects to the marine life through the introduction and construction of the MFB to the Tonle Sap. All construction of the bridging system will be based on land, thus eliminating any potential contaminants and reducing any waste material from entering into the water supply during the construction process.

All assembly materials have been specifically treated and selected for the MFB’s construction, to minimize impact they pose to the sensitive marine ecology of the Tonle Sap, once the MFB implements.

Furthermore, the plastic barrels, which are the buoyancy device for our MFB design, are made out of recyclable materials and not severely distorted, thus will have no adverse environmental effects, and can be recycled and reused even at disposal of the MFB.

1.2 Sustainability of Materials

Due to the water exposure treatment, the wood can be immersed in water and will not show signs of warping and deterioration, as would if normal timber, if it were not treated. The long life expectancy of the timber is just one of the specifications of the MFB that make it a long-term sustainable advantage over its competitors for the Tonle Sap Region.

1.2.1.1 Polyethylene Drums

The drums used as the floatation devices have been molded from a polyethylene thermoplastic (River Lake Sea, 209), which exhibits exceptionally durability. These drums were selected, as they were very strong and lightweight, and furthermore would not rust, as it will be constantly subjected to water in the wet season.

However, since plastics will tend to breakdown from over exposure to the harmful ultraviolet light rays from the sun (Layfield Geosynthetics, 2009), and since the top of the drums will be above the waterline, an ultraviolet stabilized polyethylene material is used for the floatation devices in the bridge design.

It can potentially take centuries for Polyethylene (StateMaster, 2008) to fully breakdown, because of the synthetic polymers they are made from, thus their chemical stability; however if any faults were to happen to the drums, they can be recycled.

Thus, the material’s inactivity will mean little-to-no adverse affect when introduced into the bridging system in the Tonle Sap, providing a long-term sustainable component for the bridging network. The UV stabilizers only enhance their sustainability.

1.2.1.2 Wooden Planks

Although the MFB is designed to allow the polyethylene drums to be fully submerged in the water, the wooden planks used as decking along with the support beams that hold the MFB together are not underwater, though it will be constantly subject to water through waves, as well as rain. The treatment of wood with Tung Oil is intended to increase its life, so can be used in an aqueous environment (Food and Agriculture Organization of the United Nations, 2007).

As this bridge is going to be used quite frequently throughout the wet season, a good oil that stands up to the harsh conditions needs to be chosen. Although there was a range of products that provided water resistance, only Tung Oil could do it at a relatively cheap price, as well as being easy to obtain (Sankey, 2009). Tung oil comes from the Tung tree, and is a part of the flora of Cambodia’s neighboring country, Thailand (Thailand is directly West of Cambodia) (National Herbarium Nederland, 2009).

However, although a simple process, to maintain the water-resistance, the Tung oil needs to be reapplied every two to three months (Haymes Paint, 1998). The oil just needs to be re-applied to a clean surface and there is no need for the wood to be sanded down. Furthermore, pure Tung oil is a relatively safe product to use, as it is non-flammable and non-toxic (Refinish Furniture, 2009).

1.2.1.3 Steel Brackets

1.2.1.3.1 Corrosion Resistance

To connect the overall structure of the design, steel brackets were designed to connect the polyethylene drums to the wooded beams. Steel is a strong metal that is capable of doing its job well; however, steel can rust quite rapidly and will potentially be useless in holding the design together if this occurs. Steel will rust when subjected to moisture and oxygen (Holleman, 2001), thus the harsh wet condition of Cambodia and the oxygen in the atmosphere is the ideal climatically conditions for corrosion.

Thus, a layer of corrosion resistant paint is applied to the metal brackets (Suzuki, 1989), meaning the surface of the metal bracket is not exposed to the water. Therefore, the metal is unable to corrode and provides a sustainable join. Furthermore, the corrosion resistant paint includes rust inhibitive pigments, such as marine-grade primocon antifoul (MarineStore, 2009), ensuring that the steel lasts for the duration of the bridge’s service. Furthermore, it only needs to be reapplied yearly, with an ordinary paintbrush against a mildly sanded surface (preferably 40-80 grip sandpaper), requiring approximately eight hours to fully dry before it can be subjected to water (Micron).

If rust does appear on the steel brackets they can be recycled to a scrap metal yard where a kilogram of scrap steel can be sold for approximately 500-750 riel (approximately 15-20c AUS) as “scrap metal” (CAMNET, 2004).

1.2.1.3.2 Weld

The weld that joins the steel brackets together, which supports the floatation devices, provides strength, comparable to the original strength of a metal (Du, 2000). This strong join will provide strength for the bridging system over a long period.

1.2.2 Disposal

1.2.2.1 Polyethylene Drums

As polyethylene drums can potentially take centuries to break down (StateMaster, 2008), there is no need for them to be replaced. However, if holes and cracks do appear in the drums, the polyethylene drums can be recycled accordingly (Concord CA, 2009).

1.2.2.2 Wooden Planks

To dispose of the wooden planks that are no longer capable of doing their job safely, it is best that either the wood is:

v Reused for other purposes that is suitable, but isn’t dependent on the wooden planks being of paramount quality, such as small fences; or

v The treated wood can be recycled

It is strongly recommended that the treated wood must not be burnt in open fires. Although Tung Oil is non-toxic, it can potentially emit toxic chemicals in the fumes and ash when burnt (SWTOP, 2008).

1.3 Maintenance Strategy

The maintenance inspection will provide systematic guidelines that must be implemented in order to achieve the maximum functional usability of the bridging system and all it offers to the community.

Initial inspection will be conducted by qualified personnel, to ensure that the correct construction method and techniques are of a satisfactory standard. This will reduce stress on susceptible components of the MFB segments, once implemented into the community.

1.3.1 Inspection Methodology

1.3.1.1 Initial Material / Construction Inspection

The correct initial construction process is paramount in the long-term sustainability of the MFB segments.

The qualified personnel will review that:

v All materials used are the correct material as specified by the design: If incorrect materials are used for the construction of the MFB’s, detrimental effects may occur, as the incorrect materials will be unable to adequately support the anticipated loads, and the environmental conditions without deterioration;

v Defected materials will not be implemented in the construction process: Material defects and incorrect sizing will produce a “weak point”, which will be unable to support loading conditions, and hazardous environmental conditions. Despite it may be difficult to achieve, an optimistic target should be General Electric CEO, Jack Welsh’s “Six Sigma Program” (Antony, 2008);

v Materials dimension are made to the design specification: Components must be assembled to design specification for functionality and strength purposes;

Any poorly constructed bridging system will likely be seen by the Tonle Sap community as disastrous, as seen with the collapse of the Tonle Sap’s “25m Bridge”. Inspecting materials and construction integrity will reduce the likelihood of material and assembly failure, thus preventing any consequential safety hazards, and complex public relations issues that may result.

1.3.1.2 Routine Maintenance Inspections

Routine maintenance checks will be completed three times a year once the bridging systems have been introduced into the Tonle Sap community. This strategy enables any repairs to be made to the MFB components before, whilst, and after they are most used (during the wet season). Furthermore, other maintenance’s and adaption’s can be made accordingly.

1.3.1.2.1 Inspection 1: Pre Wet-Season

All sections of the MFB are to be inspected before the wet season commences, for:

v Material integrity

v Correct assembly

1.3.1.2.2 Inspection 2: During the Wet-Season

Samples of the MFB, generally of a size square root of the population (Baldwin, 2007), are to be simple randomly sampled (Yates, 2008) and inspected from various areas within the Tonle Sap, for:

v Material deterioration

v Material joints

If from within the samples there are consistent maintenance problems, inspections of a larger sample may need to be made (even the entire population). However, general maintenance and repairs will be based on accessibility, and the extent of the damage.

1.3.1.2.3 Inspection 3: Post Wet-Season

Samples of the MFB are to be simple randomly selected and inspected from various areas of the Tonle Sap, for

Because the MFB will be less used post wet-season, more vigorous checks can be achieved at this time of the year. An annual design review will occur, with recommendations, possibly improvements and adaption’s, to be made to the existing bridging system.

1.3.2 Special Maintenance Considerations for Susceptible Componentry

1.3.2.1 Weld Inspection

The weld will be inspected for join integrity upon all checks. This is vital in the construction of the bridging system as it provides the fundamental support for the buoyancy device. This will be maintained and repaired to ensure operational use of the bridging system.

The protective coating of the metal bracket is vital in corrosion prevention. This will be reapplied upon maintenance checks, subject to wear, to ensure the protection of the metal brackets, thus prevent rusting, hence material failure.

1.3.2.2 Bridge Loading

Despite the bridging system can only be subject to specific conditions (that is, only people and household items; and strictly no vehicle), because Cambodians may not follow civil regulations (European Commission, 2009), bridge loading has to be tested from time-to-time to ensure no safety issues will arise as a result of using the bridge.

1.4 Ethics

In designing the MFB, the engineering team faced little to no ethical dilemmas, riding on the back of a culture of “corporate social responsibility”, also known as “CSR”.

The MFB benefits Cambodia in terms of the “3 E’s”:

v Economy, both indirectly and directly, as mentioned in 2

v Environment, by the use of carefully chosen materials

v Entrepreneurship, by directly encouraging and inspiring other Cambodians; and indirectly by lowering costs of travel, thus lowering barriers to entry (to education, or business)